Maintenance: Living with a tank-less water heater

We get very hard water out of our well. I mean water so hard the charts put out by water-softener companies don't even go that high. And no, we don't have a water softener. There is space, plumbing and power out in the well house for it, but we haven't broken down and actually bought one yet. A large part of that is we just don't like softened water but another, big, consideration is that we would nearly double our water consumption with the back-flush cycle that a softener would require given the hardness of our water!

So right now we live with the consequences. And since we use a tank-less water heater those consequences can sneak up on us if we don't watch it.

We really like the tank-less technology for hot water. As long as the power holds up you can't run out of hot water yet the only time it uses any energy at all (For us that's electricity because we didn't install a propane system in the barn.) is for the few minutes a day we're actually running hot water. The rest of the time it just sits there. But since the innards' of a tank less water heater are actually quite small, scale buildup is noticeable long before it would be in a tank type system, although both will be killed by unchecked scale. In fact we are now the proud owners of two tank-less water heaters because the original was killed, though I managed to revive it.

The original has two pots the size of large coffee mugs with coiled heating elements inside them. These pots are configured in series so the second receives water already heated in the first and makes it even hotter. Over the course of two years or so it gradually got less and less effective. After installing a new heater about 6 months ago I dismantled the original (Hey, it already didn't work too well so I couldn't make it much worse could I?) and found that the heating elements were completely coated in scale and the second pot, the hottest one, was almost completely choked with the stuff. A few hours of work cleaned them right up and now we have a spare heater on the shelf.



Our new water heater. There is a shutoff
valve out of sight to the right on both
the hot and cold lines. The blue conduit is
for the electrical.

In the mean time we replaced original with a new one that has two small pipes inside configured in parallel which keeps their temperatures even. Each of these has a straight heating element right down the center for a more laminar water flow which will also, hopefully, cut down on stubborn scale buildup. The new heater also has an output temperature sensor and a digital thermostat which really helps keep the water temperature steady when several faucets are opening and closing at the same time, something the input temp only sensing units are not quite so good at.

(One trick to living with a tank-less water heater is to set the water temperature to 110-115 degrees and when you want hot water, like when taking a shower, or hand-washing dishes, just open up the hot water valve and forget about the cold.)

Having seen the state of the innards of the original heater, despite flushing it out a couple times a year, I now flush the new one once a month. I do this at the same time we do several other monthly chores around here. (We actually have a spread sheet with a whole bunch of maintenance items to be done monthly; cleaning the dishwasher filter, checking all tire pressures, lubing the gate opener, etc.: which takes about 6 hours to complete, usually spread out over two days since we are retired and people of leisure now.)





Our flush kit. Notice that the handle of the bucket has been
bent. This is so we can hang the bucket above the level of the
water heater.

To make the flushing process easier we built a 'flush kit' with some left-over PVC, a 12 volt self-priming pump, a small bucket and a couple of the same flexible-armored heater connection pipes used to connect the water heater into the plumbing. By the way, the instructions for installing both of the water heaters required a shut-off valve on the cold water side but not on the hot water. Don't believe that! The single-handle cartridge type faucets we almost all use now will back water up into the de-pressurized hot water plumbing so a valve is needed on both sides!!


 The first step in our monthly flush is to pour about a half gallon of white vinegar into the bucket. The blue tape on the side of the bucket marks the proper level to make this easier. Then we remove all the faucet heads and drop them in the bucket to soak for about an hour. After an hour or so the vinegar will no longer be bubbling as it eats away at the mineral deposits. This gets the faucet-heads nice and clean and shiny. At the same time we get all those little screens flushed of any loose scale, though I have to remember to pull the hoses off the back of the washing machine once in a while and clean those screens out too or it starts taking longer to fill the machine that is does to agitate the clothes!









Then it's time to focus on the water heater. First step is to close the shutoff valves and remove the cold and hot pipes from the bottom of the heater using a couple small containers to catch the little bit of water that drips out. The pipes from our kit are then attached to the water heater and the other end of each is hooked over the edge of the bucket, which still has that original half gallon of vinegar in it.

The bucket is then hung by the handle, custom bent for just this purpose, from a couple of small screws installed in the top of the shelf unit. this puts the bucket above the level of the water heater so when vinegar is pumped in it won't drain back out into the bucket.

By the way, in between flushes the 'kit' is stored there on top of the shelf unit.

 

The wire for the pump is long enough that it can reach to the floor and be clipped to a battery, usually the battery for starting the gas powered fire pump, but lately I've just been using an old 10 Amp battery charger for power instead.

The battery charger will only run the pump for about 20 seconds before cutting out and needing to rest for a few minutes, but that's plenty of time to fill the water heater with vinegar. Then I just leave it sit in there to do its thing. I also leave the water heater power on during this so when it sees the vinegar flowing it doesn't know its not water and the heater elements comes on. Hot vinegar is more effective at eating the scale than cold.

That first run of the pump flushes out chunks of scale and the vinegar starts bubbling furiously as it works on them. The same thing is happening inside the water heater to the scale that was too stubborn to let go.

About every 20 minutes I run the pump for another 15 or 20 seconds to stir things up and reheat the vinegar. After an hour or so of this, depending on how distracted I get, all the chunks in the bucket have dissolved and the vinegar has stopped bubbling. I assume the same has happened inside the water heater so then it's time to remove the flush kit and hook the heater back into the plumbing, making sure to flush any residual vinegar out of it before taking that next shower!! A trick I use for this is to only hook the cold side of the heater (The right-hand connection,) back into the plumbing then remove the hot side of the flush kit from the bucket and lay it in the utility sink, just off the left side of the photo above, and open the cold valve for a few seconds and rinse the heater out.

There's a lot of wait time in this process, waiting on the faucet-heads to soak and waiting between pump runs for the vinegar to work on the inside of the water heater, so actual time spent on the whole process is something like 20 minutes and it takes about $1 worth of vinegar. At that rate it will take about 40 years to recoup the cost of a water softener!






This is what the inside of the bucket looks like before pumping vinegar into the water heater












This is what it looks like after that initial run of the pump! That's chunks of scale down there in the bottom and it's only been a month since the last flush!